1. Field of the Invention
The present invention relates to apparatus for protecting towers and other structures from lightning strikes. More particularly, the present invention relates to preventive devices for avoiding the damaging effects of lightning strikes.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
Lightning conceivably may have provided humankind with a first source of fire, but lightning has otherwise been a destructive force throughout human history. Strategies and apparatus for reducing the likelihood of damage by lightning are fairly old, including, for instance, lightning rods that have been use for approximately 200 years. While the use of such rods and other precautionary steps and safety devices reduce the damage and injury that would otherwise result from lightning today, it remains an enormously dangerous natural phenomenon that claims hundreds of lives worldwide every year and destroys a substantial amount of property. Somewhat paradoxically, advances in other areas of technology have increased, rather than diminished, the damage caused by lightning. This is because relatively low voltage and current levels can damage integrated circuits and other modern electronic components, with the result that many electronic devices are more susceptible to lightning damage today than ever before. Many devices to which microprocessor technology has been added are more susceptible to lightning damage as a result of such improvements. Additionally, lightning is capable of inducing substantial currents not only in electrical circuits directly struck by it but also in circuits located within the magnetic field induced by a nearby lightning strikes, giving each strike enormous destructive potential.
One of the most common areas of lightning strikes are large telecommunications and camera towers that extend upwardly from the earth. Typically, such towers include an electronic device at the top which serves to transmit or receive information. Since lightning will follow a path of least resistance on its way to the earth, the towers are very attractive to lightning.
Whenever lightning strikes a tower, an enormous amount of damage is created. Typically, the electronic device at the top of the tower is completely destroyed by the lightning. Furthermore, the structure of the tower and other associated electronics at the top of the tower can become damaged. Repair efforts on the tower are often time consuming and expensive. Typically, complete replacement of the electronic device at the top of the tower is required. As such, it is very important to develop a device which resists or prevents lightning strikes.
It is known that as a storm approaches, it will be highly charged with either positive or negative ions. In certain circumstances, the front side of a storm can be charged with positive ions and the back side of the storm can be charged with negative ions. As the storm would move through a particular region, the earth will be oppositely charged to that of the storm front. For example, if the storm is highly charged with positive ions, then the earth will be highly charged with negative ions. When metal structures are positioned on the earth (or in the water, as in the case of oil rigs) the strong charge of ions in the earth will flow through the metallic structure and upwardly above the earth. As such, a charged metal structure will present an attractive strike location for any lightning that may occur from the storm.
There exist devices known as differential field mills or field meters which can sense the polarity of an approaching storm and the intensity of such electrical field. Heretofore, these devices have not found use in preventing lightning strikes affecting metallic structures extending above the earth.
The present inventors were also the inventors of U.S. Pat. No. 5,694,286, issuing on Dec. 2, 1997. This patent was for a lightning protection device which relies on negative ion production at the top of the tower. The negative ion production device serves to produce solely negative ions around and over any electronic devices positioned on the towers. A special type of grounding rod, commonly known as an AUGERROD™, engages the earth so as to be conductively connected to the earth. An electrical line connects the grounding rod to the tower. A shield member is connected to the tower and extends over the electronic device on the tower. The negative ion production device is connected to the shield member so as to pass negative ions through the shield member. The negative ion production device can be one or more batteries that are connected together and have a negative terminal connected to the tower and a positive terminal connected to the electronic device.
Although, this device has been proven to be generally effective against the damaging effects of lightning strikes, it was found that a certain number of storms were negatively charged. Under such circumstances, the mere production of negative ions at the top of the tower would be attractive to the positive ions following the storm in the earth. Additionally, it was found that the use of batteries for the production of the negative ions was a less efficient approach than the use of a readily available alternating current power supply. It was further found that although the device was very effective at preventing lightning strikes to the electronic equipment located at the top of the tower, a large proportion of the tower would be available to a lightning strike below the upper portion of the tower. As such, a need developed so as to protect the entire tower from the possibility of the lightning strike, especially where the storm front was negatively charged.
It is an object of the present invention to provide a lightning protection device that effectively “masks” the metallic structure from lightning strikes.
It is another object of the present invention to provide a lightning protection system and method that serves to avoid damage caused by lightning strikes.
It is a further object of the present invention to provide a lightning protection system and method that is easy to use, easy to install and relatively inexpensive.
It is a further object of the present invention to provide a lightning protection system and method that can be retrofitted to existing towers and metallic structures.
It is a further object of the present invention to provide a lightning protection system and method which will be adjustable to the polarity of a storm or the magnitude of the storm.
These and other objects and advantages of the present invention will become apparent from a reading from the attached specification and appended claims.